Diffusion model of sulfate ions in concrete based on pore change of cement mortar and its application in mesoscopic numerical simulation

Abstract

Sulfate attack is a major cause of the deterioration of concrete structures.Accurately predicting the temporal and spatial distribution of sulfate ions in concrete is the basis for revealing the mechanism of concrete performance deterioration caused by sulfate attack. In this article, based on the pore change caused by sulfate damage to cement mortar, a diffusion model of sulfate ions in cement mortar considering changes in surface concentration was established. Furthermore, a two-dimensional mesoscopic concrete model composed of cement mortar, coarse aggregate, the intrafacial transition zone (ITZ) and macroscopic defects, which can reflect the real aggregate shape, was constructed to study the diffusion of sulfate ions in concrete. The correctness of the model is verified with existing experimental data, and the model is further studied. The results show the following. (1) The average value of the calculation results of multiple sets of models can be used to eliminate the influence of the randomness of the construction of the two-dimensional mesoscopic concrete model. ( 2) With increasing stone content, the corrosion depth increases, but the average concentration at a given location decreases. (3) With increasing sulfate solution concentration and water-cement ratio, the sulfate ion concentration and the corrosion depth in concrete increase.

Study on rust layer distribution of cracked segment at tunnel arch waist under stray current and chloride ion corrosion

“…In Equation ( 5), c t (mol/m 3 ) is the total content of chloride ion in concrete at depth x and time t. The chloride ions mainly exist in concrete in two forms: free ions and bound ions, 24 but the medium causing corrosion on the surface of reinforcement is only the free chloride ions. At present, the most commonly function to describe relation between bound chloride ions and free chloride ions is the Langmuir adsorption isothermal equation as shown in Equation (7).…”

“…Under the action of stray current, the diffusion rate of chloride ion to the surface of segment rebar will occur change, the corrosion rate of segment rebar will increase greatly. 7,8 As the rust layer of rebar is three to six times of the original volume, 9 corrosion-induced cracks will result in reducing the bearing capacity of the tunnel structure, 10 so it is necessary to study rebar rust layer of shield tunnel contained cracks under stray current and chloride ion corrosive environment.…”

Effect of groundwater decline on plant induced by tunnel excavation and calculation of ecological water level based on SPAC model

“…The intelligence and informatization of tunnel drainage are development directions of intelligent construction of the tunnel. High underground water pressure and corrosive ions in groundwater can affect the safety and durability of tunnels [1][2][3]. In the past tunnel construction, the treatment of groundwater was mainly based on drainage, which could significantly reduce the water pressure of the tunnel lining [4], prevent water inrush [5], and ensure the safety of the tunnel structure [6].…”

Study of the damage characteristics and corrosion mechanism of tunnel lining in a sulfate environment

“…Thus, lining corrosion problems are a growing concern for scholars all over the world. Among various corrosion factors, sulfate is one of the most important causes of tunnel lining corrosion (Zhuang et al, 2022;Zhang et al, 2023).…”